1. Technical Field
The present invention relates to packaging articles or groups of articles by means of packaging elements having printed marking, with the wall of the element being made of plastics material. The term packaging xe2x80x9celementxe2x80x9d as used herein should be understood in its broadest sense, covering in particular rigid or semirigid containers (bottles, blisters, boxes) and flexible films, and in particular heat-shrink films.
2. Background Art
The extensive development of distribution circuits is raising more and more problems for packaging professionals in their fight against misappropriation, whether of pharmaceuticals, perfumes, or food products in particular. Major manufacturers often have exclusive distributors, and it has been found that certain distributors sell off a portion of their stock at a substantial discount, thus enabling products to be put back on the market at low prices. This problem is further complicated by goods traveling across national borders where the legal and tax regulations often differ between countries. Such movements naturally tend to destabilize both distributors and manufacturers. In order to counter this practice of so-called xe2x80x9cgrayxe2x80x9d or xe2x80x9cparallelxe2x80x9d markets, which has been taking on worrying proportions in recent years, it would seem to be essential to develop concepts of product traceability.
Traceability serves to identify a particular product at various points in a unique manner, and considerably facilitates data management. Nevertheless, fraudulent handling of goods makes it necessary to provide markings, and in particular coded markings, that must be as discreet as possible so as to preserve product traceability, and thus avoid any modification or destruction of the packaging. Thus, various reading techniques have been developed, for example using interlaced bar codes (xe2x80x9ctwo out of fivexe2x80x9d) or other codes, or using electronic chips, suitable for being read by an appropriate reader machine which the manufacturer or the distributor possesses. Unfortunately, these codes are generally easily spotted by crooks who can then remove them or tear them off. When use is made of packaging films or containers, or indeed of heat-shrink sleeves made of such films, the code is generally printed on the inside face of the packaging element, i.e. the face that faces towards the article. Nevertheless, a knowledgeable crook can easily cut open a packaging element of plastics material and thus gain access to its inside face in order to alter or erase the printed code.
The technical problem that the invention proposes to solve is that of creating a concept of marking a packaging element of plastics material in such a manner as to avoid the codes used being identified, so as to preserve them from destruction, while nevertheless guaranteeing that the packaged products can be identified and traced.
It might be tempting to use techniques that are already in use on packaging made of paper or card, for example printing codes using sympathetic ink, i.e. a colorless liquid which writes a secret text or an encrypted code that appears only under the action of heat or of a reagent. Such ink is also used in the field of authenticating documents: document U.S. Pat. No. 4,227,719 thus describes a technique for providing protection against photocopying, whereby a warning pattern printed directly on the document is used, and is covered in camouflage printed with ink at a density that is selected to be below the critical threshold of the photocopier, such that any photocopy of the protected document automatically causes the warning pattern to appear on the copy.
Unfortunately, this leads to a difficulty that is not easy to overcome, and that is inherent to depositing sympathetic ink on the face of a wall of plastics material, regardless of whether that wall is rigid, semirigid, or flexible, whereby the ink remains visible to the naked eye, in particular when observed in grazing (or incident) light. Thus, even if the encrypted code cannot be read immediately by the crook, its location can easily be found, and consequently the zone that has received a code printed in sympathetic ink can be destroyed. This difficulty does not arise with paper or card because cellulose fibers provide good absorption of the pigments in sympathetic ink, thus making the printing invisible.
An object of the invention is thus to provide a packaging element with printed marking in which the wall of the element is made of plastics material, which can either be essentially transparent, or else bulk-tinted, and on which the marking is not identifiable, while nevertheless being easy to read by authorized people having appropriate reader means, thus guaranteeing that products can be identified and traced.
According to the invention, when a wall of a packaging element made of plastics material is essentially transparent, this problem is resolved by means of an element having marking printed in sympathetic ink on a face of said wall, said marking being sandwiched between a primary dispersing screen deposited on said face and on which said marking is printed, and an overprinted dispersing screen covering the marking and at least that zone of said face surrounding said marking so as to make the marking undetectable.
Under such circumstances, if the film is examined from the side opposite from the marking, then the primary dispersing screen serves to prevent the marking being identified, even under grazing light, and if it is the other side of the film that is observed, then it is the overprinted dispersing screen which performs the same function of preventing identification.
In an alternative embodiment, for a wall of a packaging element which is made of bulk-tinted plastics material, the packaging element of the invention has marking printed in sympathetic ink on a face of said wall, said marking being sandwiched between said face on which said marking is printed and an overprinted dispersing screen covering said marking and at least that zone of said face which surrounds said marking so as to make the marking undetectable.
Thus, if the zone is examined from its side opposite from the marking, then the opaque nature of the bulk-tinted wall suffices to mark the marking, and if said marking is examined from the other face, then the overprinted dispersing screen avoids the marking being identified, even when examination is performed under grazing light.
Preferably, the dispersing screen is of speckled structure reproducing the structure used for printing the marking. The structure then makes it possible to bury the marking zone making it even more invisible. In particular, the dispersing screen is selected to be random so as to avoid identification by fine analysis of the surface.
It is also advantageous to provide for the marking printed in sympathetic ink to overlap at least in part identification elements that are printed on the same face. This makes it easier to spot any action taken in the marking zone in an attempt to tamper with the identification element, since that would make the product unsellable, for example when the identification elements involve legal requirements giving the origin, name, or composition of the product.
The above result is further improved if provision is made for the sympathetic ink that is used for marking to be revealed only under the action of a chemical reagent that is selected for its irreversible destructive action on the wall of the element. Any attempt at acting on the marking zone has the effect of destroying the corresponding zone of the wall in irreversible manner, and this can be identified immediately, even by a consumer paying only ordinary attention. The protection can be further refined by providing for the chemical reagent to be selected so that its destructive action on the wall of the element is retarded. The destructive action then appears only a long time after the crook has taken action.
In accordance with another advantageous characteristic, the packaging element includes additional marking that can be read under ultraviolet (UV) light, and separate from the marking printed in sympathetic ink. It is then preferable for the additional marking to be printed on the face opposite to that which carries the marking in sympathetic ink.
It is generally advantageous to provide for the face carrying the sympathetic ink marking together with the dispersing screen(s) to be the inside face, i.e. the face that faces the article or the group of articles to be packaged. This obliges the crook to cut through the wall surrounding the packaged article or group of articles in order to take action in an attempt to destroy the markings present on the inside face of said wall.
It is generally advantageous to provide for the sympathetic ink marking to be a code that serves to guarantee identification and traceability of the packaged article or group of articles. The term xe2x80x9ccodexe2x80x9d should be understood herein in its broadest sense, covering the most modern facilities for encrypting data.
The wall of the plastics material packaging element can be rigid or semirigid and can form a container, in particular a bottle, a blister, or a box.
In an alternative embodiment, provision can be made for the wall of the plastics material packaging element to be flexible and to form a packaging film, in particular a mono-oriented heat-shrink film. This is particularly advantageous when such a film is used for making heat-shrink packaging sleeves.
The invention also seeks to protect a heat-shrink packaging sleeve made using a segment of heat-shrink film which is mono-oriented and presents at least one of the above-specified characteristics, the film having two end edges bonded together along a generator line of the sleeve.
The invention also provides a method of manufacturing a packaging film having the above-specified characteristics.
For a plastics material film having a wall that is essentially transparent, the method comprises the following successive steps:
printing a primary dispersing screen on a face of the film;
printing marking in sympathetic ink on said primary screen; and
printing a dispersing screen as an overprint on said marking.
For a plastics material film having a bulk-tinted wall, the method comprises the following successive steps:
printing marking in sympathetic ink on a face of the film; and
printing a dispersing screen as an overprint on said marking.